Zinc cream to improve reliability of tuberculosis test
The results of this study have public health implications because the tuberculosis (TB) skin test is central to the problematic area of diagnosing TB infection and disease — especially in children prone to both zinc deficiency and false-negative skin-test results.
The zinc-mediated augmentation of TB skin testing may facilitate the diagnosis of adult and pediatric cases of TB in regions where micronutrient deficiency is prevalent.
First, the details.
- 50 healthy adult shantytown residents participated in the study.
- Blood levels of zinc were taken from each person.
- Each received an injection of tuberculin (5 Units) and Candida albicans antigen at different sites on one arm, which was then covered with 1% zinc sulfate cream and occlusive dressing.
- The same treatment was given on the other arm, but covered by a placebo cream and occlusive dressing.
- C. albicans was used to prove they could respond to an antigen challenge.
- After 24, 48, and 72 hours, the dressing and cream were removed, a ball-point-pen was used to circle and measure the indurations, and the sites were recovered with the placebo or zinc cream.
And the results.
- Importantly, zinc cream had no effect in persons with adequate blood levels of zinc.
- People who were deficient in zinc but otherwise healthy had suppressed skin-test reactions.
- This suppression was reversed by the application of zinc cream.
The bottom line?
Zinc deficiency is relatively uncommon in the United States, but it may occur in adults with alcoholism or intestinal malabsorption problems. It’s more important in developing countries.
The researchers concluded, “Zinc cream application corrected false-negative TB skin-test reactions caused by zinc deficiency, allowed more sensitive diagnosis, and hence facilitated appropriate treatment of latent TB infection. Topical zinc is a simple and relatively inexpensive method of enhancing reliability of the established TB skin test for diagnosing this neglected disease.”
8/5/07 12:54 JR
